Method and apparatus for grading solid materials



April 5b, 1927'. A 11,623,040

3. R. BAKER ET AL METHOD ND APPARATUS FOR GRADING SOLID MATERIALS FiledJan. 51. 1924 4 Sheets-Sheet 1 Aprily 5,1927. G. R BAKER ET AL A www@METHOD AND APPARATUS FOR GRADING SOLID MATERIALS' Filed Jan. 31. 1924 4Sheets-Sheet 2 emga @dph lanka, William Edward @660K TTOR/VEY.'

l/VVEWTORS Chaffee WlSn-d Gilerdale.

April s, 1927. 1,623,040

G. R. BAKER ET AL METHOD AND AFPARATUS FOR GRADING soLIn MATERIALS FiledJan. 31. 1924 4 Sheets-Sheet 3 INVENTORS Gerg A|?a1|ph laker, Wflh'amEdward @escom/ Charles Wfed Gilda-dale.

Afro/Mfr.' WMM@ 1,623,040 April 5 1927' G. R. BAKER ET AL I METHOD ANDAPPARATUS FOR GRADING SOLID MATERIALS Filed Jan. 51.l 1924 4sheets-sheet 4' /N VE N TURS" Georg {Qa lph emh'efv William Edward@6560K v charles wilg@ Gnafdaf.

Arm/mfr.' m

Patented Apr. 5, i927.

UNTED STATELS PATENT @lilld'i GEORGE RALPH BAKER AND W'ILLIAM EDWARDPRESCGTT, OF LONDON, AND CHARLES VJILFRED GILDERDALE, 0F NEW EARSVVICK,ENGLAND, ASSIGNORS TO ROWN TREE AND COMDANY LIMITED, 0F YORK, ENGLAND.

METHOD AND APPARATUS FOR GRADTNG SOLTD MATERIALS.

Application filed. Eanuary 31, 1924, Serial No. 689,737, and in GreatBritain February 26, 1923.

This' invention relates to methods and apparatus for grading solidmaterials.

in th-e art to which the present invention relates it is a fact that asthe size of partici-es of a powdered substance is decreased saidparticles become more and more easily influenced by air currents, andwhen an extremely fine powder is produced it may readily be carried in agentle current of air, even when the material has a high specificgravity.

ln other words the smaller' the particles of a powdered substance, themore important becomes the inuence of the surface friction of' a currentof air thereon in relation to the force of gravity. This fact is madeuse of in the separators generally used for grading iin-e powders, inwhich powderdaden vair is blown into a settling chamber, the coarsestgrade being deposited most quickly and falling near the air inl-et, thefinest powder on the other hand being deposited at the point farthestfrom the air inl-et. Diiculties .arise however where this method isemployed for very ne powders in that the air current employed has to bevery gentle and eddies due to temperature variation or other causesquickly interfere with the correct working of the settling chamber,furthermore such a device has to be very large to obtain any reasonableoutput of material.

The object of the present invention is to provide a novel and moreaccurate and positive method than at present in 'use for gradingparticles of `solid material by means of a current of air.

According to the present embodiment of our invention shown in thedrawings, currents of air in which the material to be graded isdistributed are caused to pass inwards through a revolving separatorwhere by the material and air are caused to rotate with the rotor of theseparator and to be subjected to the action of centrifugal force, theregulation being such' that the air cur.- rent overbalances thecentrifugal force as regards the smaller or light particles and thecentrifugal force overbalances the air current as regards the larger' orheavy particles so that the latter are projected outwards against theair current whereas the smaller' or light particles are carried by theair current.

In the operation of such a method the particles of solid material in theair will be acted upon by three forces, viz

Firstly, the skin friction of the .air current which has carried theminto the zone of action of the rotating member and exerts a force on theparticles tending to carry them with the air current towards the centreof said member.

Secondly, the force of gravity, and

Thirdly, the centrifugal force acting on the particles as they arecarried round by the rotating member.

If the speed of the rotating member or rotor is at all high, the forceof gravity becomes extremely small in relation to th-e centrifugal forceso that there are substantially but two opposing forces acting on theparticles, viz, that of'centrifugal force tending to carry the particlesoutward from the centre and the skin friction of the air current movingtowards the centre of the rotor. rThe smaller the particles the strongerwill be the influence of the air current when the rotor is running at aconstant speed and it will be apparent that with a given rotor speed andspeed of air current all particles larger than a certain size will berejected or driven off centrifugally, whilst `all smaller particles willbe carried by the air current towards the centre of the rotor. lf therotor speed 1s increased, still finer particles will be rejected andonly those particles of such size that the skin friction of the aircurrent overcomes the centrifugal force due to the speed of the rotorwill be carried in the air current towards the centre.

As the centrifugal force due to the speed of the rotor and the strengthof the air current passing through the lines of centrifugal force may bevaried within extremely wide limits, it will be seen that a very exactand readily controlled means of grading granulated or powderedsubstances is provided by which it has been found possible to grade veryline powders far more accurately and efciently than. by any meanshitherto known.

Furthermore a great saving in the size of apparatus is effected, duetothe fact that relatively large forces are .employed compared withgravity. ln any ordinary expansion separator an air current is usedagainst gravity and for very line powders only very gentle air currentscan ber employed, and this necessitates aV very bulky apparatus.

In this invention high air velocities can be used. to balance highcentrifugal force, so that the saine' amount of fine material can be'carried over' in a very much smaller appa',- ratus.

A further advantage is that by balancing the two large forces as statededdy currents have little or no etl'ect on the efficiency of separation,whereas in an ordinary expansien chamber they= seriously interfere withthe accuracy of grading ot very fine pow# ders.

'Ifheinvention may also be employed for separating two powderedmaterials ot ditt-erent `specific giafvitiesf andV in this case'tliepartieles'tobe separated need not necessarily bel ot ditferent sizes;

An embodiment ot apparatus tor car fying out the present invention: is`illustrated in the` accompanying drawings in which Fig. l is a vverticalcentral section. Fig; 2 is asectional elevation at right-anglesfto/Fig. 1. Fig. Eris-a7 sectional@ plan on the4 lineiA-B ot'Fig: 1, and Fig: t isa partiiall planshowin-gthetailings" chutehereinafter referred to andr with parts removed for clearness otillustration;

The" apparat-ns shown in` the idrawings compnises an'o-uterstationarycasing@ provided at thet-opwith means, showiras comprisingA a hopper ai'and worin conveyor a2', for feeding inz tiheinatlerial;y Thiscasing iscarried by a snitabl'ehollow pillar as andf is open below and shaped:toprovide av chute Z) for discharge of: tailings or heavier particlesinto whieln chnteleadsv an inlet b1 tor air trom anyy suitable source,.suoli as a cyclone seperator, it the material treated is passed theretoafter treatmentin the presentv appa rat-ns, as may possibly be done.,VLocated in the=oasing* a-is'the rotor which comprises a central`vconical: drum c' carrying a` number of radialvanes c1 bet-ween' whichareV arranged a' Series ot spaced plates or battles'c2 'shown-asinclined butv whiclr may alsobe flat, and the drum being provided aboveywith aconioal and axial outlet 03 lextending into-the' cover at ot thecasing and connected to a trunk` or pipedy which leads to afan, blowerAon other air exhausting devicei d* of-r any' appropriate kind and which,iff desired-,.mayfhavef-a delivery Z2 tothecyclone separat-erbefore-mentioned.' The vanes c preferably extend for the wholeA lengthof the rotorbetween end members formed by thepantsi 63,04 andfairontletsmay be provided on both said end members so that the .cunrenti ot ainmayK be sucked oft at'l both ends; if-rdtisired.` The tan isfshow'nasVdrivenr by. pulley. di" and belt df" from` any suitable sourceof. power.'llhebaseotY` tlie'= drum c substantially closing the end of the rotorand the rotor as aJ whole is carried by a vertical sha-tt c, carried byant-iliriotion bearings el and suitably enclosed in a tubular housing e?extci'iding through the pillar a3 and tailingsV chute I; the 'shaftbeing provided at? its' lower end within the bot-tom ot' the pillar witha pulley c3 driven by belt et from a pulley f on a. main drive shaft f1,from which also the teed worm a? is driven through belt and pulley gearj,

The cuter casing a is also Vprovided on its inner surface with' radialvvan'es -glbetween which are mounted a number of inclined platesorbatllcs g1 (which may also be flirt similarly to th-oplat'es c2 or etother required shape) the inner edges of which pass between the outeredges ofthe drum plates and extend beyond said outer edges for a shortdistance intoy the spaces between" them; Thesepla-tes' and the cutercasing carrying theniare made in halves so that they lit togetherbetween the plates c2 of the rotating member. The outer edges ot' saidplates g1 are atv varying distances from the wall of they casing a toferm gradually decreasing passages g2 from' below upwards.

Frointhe above description itz willj bev apparent that the interior ofthe rotor is sub jectedV to the suctionall effect ot the tan', tending.todraw the air and particles carried thereby towards the Centrethereo-,andi in" the operation o tthe device the material fedi intothe top ofthe casing by theworm a2 isfdirectedl byl aI depending deflector h,falls alternately ontotlieinclined:plates 02 of the rotor and g1 of` thecasing inl su'c'cession'- in a zig-zagv course, whilst therotorisrotatedl The air entering at the inletV b1 passes through the'channels between the casing platesr g1 and in approaching the rotorcarries with it the deseending material', it then crosses the regionbetween' tlieirotor plates c2` where itfis=suhjected tothe action otcentrifugal force which removes the heavier` particles; then carryingwith it the'lighter para ticlesthe air current passes up the face of't-he conical drum 0 and out atA the top tliiouglr the` trunli cl, forsubsequent delivery to the (Liyclone separator or tobc` collected insome other way.V

The above descriptionE discloses .in` zu gcneralfwa-y the function ottheapparatusbut there are other considerations for theA eiii'- cientvorlring ot the apparatus which; will now be referred to.

Inorder to obtain accurate grading"l it isV llt) important that thevelocity ofv the air curthrough the rotor should be approximately equalat allu active points'ot its surface.4 One way ot' obtaining; this re-`sult iss-:by the construction above' described` iii-which the rotor isdividedinto at number otsections byF the plates= el intersecting.: the`Aradial vanes c1 and with the axial passages# rent pasf a 01 between thelatter ensuring that the air passing through the rotor from the outsideinwards crosses the regions between all the plates at substantially th-esame velocity and travels inwards in directions passing through the axisof the rotor whilst crossing said regions. This result is assisted bythe provision of the axial out-let c2 for the rotor at one end and theconical drum c forming the hub of said roter, the base of the drum beingsituated at the closed end of the rotor and the apex of the drumadjacent the air outlet, thus ensuring that the air entering the rotortravels inwards at an approximately uniform velocity in all parts of therotor. This result is also assisted by the .fact that the hub of therotor is conical, that the spaces between the rotor plates c2 and thehub increase in an upward direction, and that the spaces bet-ween thecasing plates and the casing decrease in an upward direction.

It is also important to ensure that all particles passing` into theregion of the rotor are acted on by centrifugal force of the sameintensity, or in other words, that once the particles enter theseparation Zone of the rotor they kare positively carried roundtherewith, this result being obtained by the provision of the radialvanes e1 and plates c2 as above described.

. All portions of the material are brought equally under the influenceof the air passing into the rotor and the heavier material rejected bythe rotor is successively returned to it to ensure that all fineparticles are separated therefrom.

Such result is obtained by the relativelarrangement of the rotor andcasing plates c2 and g1 as above described since in operation and moreparticularly at higher rotor and fan speeds the heavier particlesrejected by the rotor take a zig-zag path upwards again between theadjacent edges of said plates and fall back again thereon for furthertreatment. Also the action of the centrifugal force may force thematerial over the outer edges of the casing plates 71 but the current ofair outside same will bring it back to bc further treated, theseoperations being repeated until the remaining heavier particles becomeso densely distributed in the air entering the rotor that they finallypass to the tailings chute 7).

An important feature of the action of the present apparatus is that thecentrifugal force does not merely drive or flick the material olf therotor plates o2 as in centrifugal separators of known construction butacts positively thereon at all times against the counter current of airdrawn inwards towards the centre of the rotor, and after leaving saidplates the centrifugal force practically ceases to act on the material,a

uniform and definitely controlled separation being thus obtained.

The invention also contemplates the employment of a series of apparatussuch as described above so that particles of any desired size may beisolated from those of larger or smaller size than those required. ltwill be apparent that this can be readily accomplished by presenting thefine product passing over with the air through the rotor of oneapparatus, to the rotor of a second apparatus running at a higher speed,which will reject the largest of the particles passing the first rotor.

It will be observed that in the apparatus shown in the drawings (whichis merely illustrative of one of the various forms in which ourinvention may be embodied) a continuously-flowing current of air whichcarries in suspension the material to be separated is maintained, andthis current as a whole, with all of its particles held in suspensiontherein, is positively given a whirling movement. This obviously givesto each suspended particle a certain centrifugal force, the strength ofwhich depends upon the speed at which the current is whirled.

It maintains the particle-bearing current continuously flowing radiallyof, that is inward toward, the axis of rotation. In fact, the apparatusspecifically illustrated maintains a plurality of such currents. Eachpair of adjacent vertical vanes 01 with the bottom cone c4 and top conec3, between which the vanes extend, forms in substance a duct orpassageway which serves to lead the air radially inward toward the axisof the rotor. This duct or passage encloses that portion of the current,and as the rotor revolves it causes this duct or passageway andconsequently the entire body of current enclosed by it to be rotated asa whole, and it and all air-borne particles therein are positivelyrotated at the same angular speed. As a consequence, substantially allparts of the current in such duct have substantially equal velocitiesand substantially all the airborne particles therein are subjected tosubstantially the same intensity of centrifugal force. Undesired eddycurrents with the resultant diminished effectiveness of the ajiiparatusare therefore avoided.

The vertical vanes 0l obviously act in the illustrated embodiment bothas the side of such duct or passageway and as a means for causing thecurrent to be given a positive whirling movement.

We are aware that our invention'claimed may be embodied or carried outby forms other than that illustratedand described.

lVhat we claim as our invention and desire to secure by Letters Patentof the United States is Vl. The method of grading particles of llt) iis

eiienf' continuously flowing radially' in? taeosly positivelyv whirlingsaid" euri-ent and varying at least one of said steps to' vary tli'eAIsi'zeof tlie product".

3. Tlie nietliod1 of grading particles of solid material" by tlie use ofa current' ofaii Wliieli'ris Wliiiled on an anis, eonipiisingmaintaining said* euri-ent continuously tion'n ing inwai'dt'ovird saidax'is", and simultaneously positively whirling saidieu'i'rent'bo'd ilyon said' axis in suoli manner that substanti ally all parts thereof moveat: tlie saine angular 1 speed.

Ll". Apparatus for grading 'particles of solid mateiial by means offalrcurrents in Wliieli tlie niateiial is" distributed, comprisiug'a rotorinclu-ding a Central hub, a" pl:ifv rality of radial varies mounted onsaid hub' and eild members on saidliub liaving an aX- ia'l' air outletand' between' Wliieli' tlle radial va'iiese'xtend for tli'e'Wlil length.

5; Apparatus for grading `particles of' solid inat'erial by means ofair' currents iii Wliieli the material is' distributed, comprising ai'ot'oi" includingl a centralx hub, a' pliifi'ality of radial vanesmounted on said liub and extending completely betweenI end meinbersioti'1 tli'e'liub lia-'ving an axial' aii"`oul'let', said rotor'beingdivided into a nuii'iber of sections by plates intersecting said radialvanes and provided with passages in tlie intei'ibrof therotbr'eonn'eeting all said seetioiis'witli theV air outlet aforesaid.'v

GQ Apparatus for grading particles ol solid material4- by means of air'currents in wliioli the' niateiif'ill is distributed; ve'o'inprising arotor having an aYial airoiitleft at one end and closed at tlieopposi'teeiidVy and including a conieal liu'b'l tlieA base oi" WliieliE isloeated at said elosede'ndadtlie' apex` adja'eentf said'air' outlet',aiid a phirallty of radial valles-mounted on' said hub and eX'-tendingil eoiilpletely betni'ejen eild ineiiib'ersy carried by the blib,

7. Apparat-iis for grading pal-tides o ij"` solid'niateiia-l by means ofair currents in" which" the iiiatijra1` is distr'ib'ted", comprising arotor having an axial air outlet at one end and Closed at tlle oppositeend and in? @aiding Conan hun the' basa of which: is" located atsaid'elo'eedeid andthe` apex' adi' jaa-ent: saai air outlay and ai pimaiiiy'of la: dial vaes mounted; on sai-d hub extend'- ing completely betiveene1`id` members ear! Y i'ied by tlieli'ub, said rotoi" being divided iii'toa" nuiiibeiot seetions by plates 'i'nte'iseet'ing-- said radial variesai'idlpiovided with passages; interioily' of the r'otoi" connecting aillsaidE seetions ivilih tlie aforesaid airo'utlet;

s. Appiaais: fer grading particles 0f solidv m'ate'rialfby ii'iean's ofaix* e'uiients in which tlie material distributed, Compris"` iiig arotfoi" including ai Central liub,` a pl`u' rality of iadial vaiiesmounted onsaid liub and extending completely bet-Ween end ,ineiiil bers'on said' liub and havingr an azial air outlet and ai cylindrical airelifa'mbei' enclosing the iot'oi' andpivided Witl interior# lydirected'platesY Witliiii ivliieli tlie` rotor"` reL volvesyr saidplates being so disposed that air' entering the man# apprea'ciiesaienaar inl directions' passing through its axis.

QQ fpparatfus for giadiri'g piitieles' of Sand material by nie-uis ofair cui-rents ia which the iii ateiial isdfstribiited; comprising aiot'i' ilieliitllng a Central lill'b, al plurality of1 `radialvanesuotili'te'd oil said hub and extending completely between' @iidmembers on the liub having an aXial al'r ot'lei','saidv rotorbeinlgdlvi'deftl into a' nuibe'r 'of s'eetions by*pla-tes'inteistiiigfsaid adialva'ies` and pinvid'eu with" passages' in-`the' interior of' t'lieifto" eoineetii'g all said sections ivitliftlle'aiifotlof afj'sild, and a: Cylln'tlllal ai"H cha ber enclosing thefotonV -and provided Wit' linteiiiorly direetedl platesivitllin Wliiehthe rotor i"evolvesgj said'last ment'ioiledf plite's beiiigl's'o dispsedtll'a't ali' entering' the rotor approaches" the71V latter inVdiieet'ins passing iii-insign iis axis;

1'05 Appaitus `ller y grading particles of solid ii'i'ateiii'l' byiiea'ii's of'aiiciiii'ents' in' Wliieh the iiia'teilal is'distribiited,l compi-is-` ing'a rotoi""l1aviiig ali aiial'air o'utlet atone end and ineludih'gl a" ceiitralli'ub, a plli'l'ality of radial"valles' iiiou'nted oh said Huband extending ciiiipletelyn be't'ivee'rleiid members tliereoiii, a plurality"fplateseariied;by said radial'vane's and iit'ersee'tiiigE saine tov di# vide` tile rotoi" ihtbl a?ni'iinber`- of' s'etioiisg` said platesi being provided vvitlY passages"Connecting` all Se'et'ioii'sivitli the aiifoiit iet; and a @aanraden-airengineer' enc-losing tlief rotor and provided: with" ii'itrorly direet'ed"v plates ivitliiil ivliieli die rbtbr r'e'- volves,` saidE lastmentionedr plates being so disposed`l tlill'tair" entering the rotor ap'praelies tlie latte-r in dii''etlb'iis passing tliliig'liits'af si' vend and including a central hub, a plurality of radial vanes mounted onsaid hub and extending completely between end members thereon, aplurality ot plates carried by said radial vanes and intersecting sameto di-y vide the rotor into a number of sections, said plates beingprovided with passages connecting all said sections with the air outlet,and a cylindrical air chamber enclosing the rotor and provided withinteriorly directed plates within which the rotor revolves, said lastmentioned plates being so disposed as to leave a progressively smallerair space between their exterior edges and the wall-ot the air chamberas they approach the air outlet.

12. Apparatus for grading particles of solid material by means ot' aircurrents in which the material is distributed, comprising a rotorrevolvable about a vertical axis and having an axial air inlet at oneend and an axial air outlet at the other, said rotor including a centralhub, a plurality ot radial vanes mounted on said hub and extendingbetween end members thereon, a plurality of outwardly directedl inclinedcones on the rotor intersecting the radial vanes, a cylindrical casingsurrounding the rotor and a series ot' stationary tunnel shaped cones inthe casing located to alternate with the inclined cones on the rotor,the inner diameter of the stationary cones being smaller than theoutside diameter o the rotor cones whereby on material being fed bygravity from the top ot the apparatus and air entering from below, thematerial passes through the apparatus in a zig-zag course, falling iirston a rotating cone then on a stationary one Yfrom which it slides downagain onto a rotating cone and so on, being thoroughly separated by thecurrent ot air being drawn into the rotor.

13. An apparatus for grading solid inaterial carried by acontinuously-iiowing current of air comprising a plurality ot' rotatablevanes arranged to whirl said current positively, and means arranged tocause substantially the entire body of said current to pass radiallyinward from without the path of travel of said vanes.

14. An apparatus for grading particles ot' material from a current ofaiil carrying said particles in suspension, comprising a duct enclosingsaid current and leading the same inwardly toward an axis of rotation,means ior bodily rotating said duct and current on said axis, and meansfor maintaining the tlow oi' said current continuously.

15. An apparatus for grading particles of material from a current ot'air carrying said particles in suspension, comprising a duct enclosingsaid current and leading the saine inwardly toward an axis of rotation,means ior bodily rotating said duct and current on said axis, means :tormaintaining the iiow of said current continuously, and means tor varyingat least one of said elements to vary the size of the resulting product.

16. An apparatus for grading particles ot solid material carried by awhirling air current, comprising conducting means arranged to lead saidair radially inward in such inanner that substantially all parts or"said current shall have substantially equal velocity, andcentrifugally-acting means for positively whirling said current in suchdirection that substantially all air-borne particles` therein shall besubjected to substantially the same intensity of centrifugal force.

In witness whereof we have signed this speciiication.

GEORGE RALPH BAKER. WlLLIAIVl EDWARD PRESCOTT. CHARLES WILFREDGL'DERDALF..

